Plastics have revolutionized farming techniques and common use in the form of films for padding, greenhouses, tunnels and greenhouses. Further developments in plastic greenhouses have focused on modification of the optical properties based on the effects caused by different types of radiation in the crops (^{Danserau et al., 1998}; ^{Lee et al., 2000}). Light is the main factor for plant growth as a different quality and quantity of light perceived species are determined variability in the structure and productivity, radiation is quite an important element for greenhouse climate control that significantly affects the temperature (^{Cázares and Figueroa, 2003}).

A change in the physical and optical properties of plastic films covering greenhouses properties may change transmitted light spectral composition which modifies the development of the plant, in some cases to increase the yield and quality of agricultural production and other cases, the opposite may occur (^{Rajapakse et al., 2000}).

Since it is possible to manipulate the adaptive responses of plants, changing environmental more sensitive to the factors, the horticultural industry and plastics have emphasized the study of radiation (^{Samaniego et al., 2002}), because the amount and quality of the light transmitted by the plastic affects plant growth and a decrease in these variables have a negative effect on the crop as it has been shown that the intercepted light intensity affects the rate of growth of the plant, for is directly related to the photosynthetic process (^{Cerny et al., 1999}). Focusing on microclimate control, it is important to reduce the high temperatures and maintain proper humidity for production (^{Medina et al., 2010}) as the temperature increases are considered a limiting factor in the development of vegetables at which, in order to optimize the quantity and quality of light for plant growth, has worked on the development of new plastic covers containing different fluorescent dyes or photo-selective, directly impacting the productivity of crops ( ^{Hemming et al., 2006}; ^{Espí et al., 2006}).

Based on the above, in the present work was presented as objective, the evaluation of a modified film with nanoparticles and fluorescent pigments in the growth and development of tomato plants, as is necessary to develop plastic covers that modify and allow greater dissemination of photosynthetically active radiation that impacts on plant responses and therefore these changes are reflected in better growth and crop productivity.

This work was performed at the Center for Research in Applied Chemistry, located in the city of Saltillo, Coahuila, in which two kinds tunnel greenhouses were established, one indoor with conventional plastic installed, and the other with a modified cover, using nano-particles and fluorescent pigments (CIQA). As experimental material, seedlings of tomato (Solanum lycopersicum L.) variety "El Cid" which were sown in trays of 200 cavities using as substrate peat moss and perlite (70:30) these were used, transplanted when they had the ideal size, the transplant was performed on the floor in each greenhouse, using plastic mulch and ground cover bicolor white background fertilization was applied, and started flowering the nutritional needs were met through fertigation.

During the development of the crop was carried out pruning and guiding, and the implementation of preventive plant protection products. The measurement of photosynthetically active radiation inside the greenhouses and the temperature was performed using a type sensor Quantum, Q16533 model LI-COR brand, the temperature was measured with Hobos sensors Onset brand, readings were taken throughout the day, the data collected from both devices were stored in a data logger model LI-1000 LI-COR mark for later download.

7 Samples were taken every 10 days during the growing season, after 20 days after transplantation of basal stem diameter, height, leaf area and biomass accumulation was determined at each reporting date, the measurement was also performed equatorial diameter of fruit and yield per plant was obtained.

A tape measure was used and for obtaining plant height was measured from the baseline to the apical growth, while for the determination of biomass accumulation, the aerial part of a plant was taken and placed in a drying oven for 48 hours at a temperature of 60 °C, then the total dry weight was obtained. The leaf area was obtained by peeling the leaflets of the leaves and passing by a leaf area meter mark LI-COR 3100, stem diameter was measured at the basal portion thereof, with a vernier.

For the evaluation of the equatorial diameter of the fruit were considered four samples of all cuts made using 10 fruits of each greenhouse and for yield was considered the fruits of all the cuts made on 10 plants randomly distributed inside the greenhouses.

The experiment was set up using a completely randomized experimental design with two treatments and three replications, where treatments were films for greenhouses and considering a plant in them as a repetition. For data analysis the statistical package SAS was used (^{SAS institute, 2001}).

Comparing the maximum readings of photosynthetically active radiation inside the greenhouses and abroad, we can see difference between them (Figure 1) these values in radiation generally occurred between the two past one p.m., being abroad greenhouses where the highest values, followed by the greenhouse with conventional plastic and with lower topped with CIQA plastic greenhouse values were observed, it was also observed that on days where low readings for this variable were presented, the difference between radiation inside the greenhouse is reduced, the highest reading on the outside radiation was 1 986 mmol m-2 sec-1, while for conventional plastic greenhouse was 1 705 mol m-2 sec-1 and the modified cover was the highest value of 1 132 mmol m-2 sec-1. These values are presented on different days the minimum values in these readings were 234.4 and 163.1 mol m-2 s-1 for the greenhouse on conventional film and CIQA respectively.

Figure 1 Peak readings of photosynthetically active radiation inside and outside of two greenhouses with different covers during tomato crop cycle. 

By comparing the maximum temperature readings inside the greenhouses difference was observed between them (Figure 2), being in the conventional greenhouse where the maximum values for this variable are presented, while the greenhouse film CIQA and abroad, lower values are presented, the peaks in temperature during the day were presented around 12 at 3 pm where the highest temperature reading with conventional plastic was 40.8 °C, while for the film was CIQA 38.6 °C and abroad a value of 36.4 °C was presented.

Figure 2 Maximum temperature readings inside and outside of two greenhouses with different covers during tomato crop cycle. 

We also found that, the temperature was influenced by the transmitted radiation inside the greenhouse, since the higher the radiation, the temperature increased. ^{Peil and Galvez (2004)} indicated that high brightness values limit the production of greenhouse tomatoes due to the high temperatures reached inside the greenhouse.

According to the analysis of variance performed to the stem diameter, no significant differences between plants grown in greenhouses with different plastic films (Figure 1) to give final values of this variable 17. 87 mm for plants grown in the greenhouse were found on conventional plastic and 18.88 mm for those grown under plastic CIQA. These results agree with those found by ^{Grijalva et al. (2011)} in different genotypes of tomato plants grown in the greenhouse which were 17.5 ± 2 mm. In relation to plant height significant difference was found in the first sample, with plants under greenhouse CIQA film that showed the highest height with a value of 54.33 cm, while the conventional plastic plants developed with a height of 47.33 cm.

Over the next four samplings there were no statistical differences between plant height in both greenhouses presented to sixth sampling where a highly significant difference between treatments where the greenhouse with conventional film featured plants with height 252.66 cm, and the film greenhouse plants CIQA induced in a height of 231.66 cm. Similar heights are reported by ^{Ortega et al., (2010)} who found plants of 250 cm in tomato plants at 75 DDT grown under glass. The results of last sampling conducted showed no differences between treatments and final heights were 286 cm in greenhouse plants with conventional plastic and 279.6 cm for plants in the greenhouse with plastic CIQA.

In this paper, the modified film reduced the amount of light transmitted about 50% compared with the exterior, the results found during the first sampling coincide reported by ^{Conover and Flohr (2003)} who found that, the height of tomato plant 'Pixie Hibryd II' was statistically larger in the maximum level of shading (50%), but does not match with the following samples, even for the sixth sampling where plants of conventional greenhouse show greater height in comparison with the plants developed under the CIQA plastic.

Table 1 Analysis of variance and mean comparisons made to stem diameter, height, leaf area and biomass accumulation of plants grown in the greenhouse under different plastic covers. 

The variable leaf area for growing tomatoes, also showed no differences in sampling dates; however, an increase in leaf area was observed over time, ^{Segura et al. (2011)} reported that leaf area of tomato plants grown in the greenhouse at 60 DDT was 1 456.89 cm² these values are lower than those observed in this study, since the values corresponding to that date (sixth sampling ) were of 1 862 cm² for greenhouse plants with conventional plastic and 20 871 cm² for plants grown under plastic cover CIQA. The results of this variable for the last sampling were 27 358 cm² and 32 817 cm², respectively. It has been reported that, the increase of the incident radiation in the cultivation of stevia, generates increases in leaf area; however, this effect was not found in tomato crop since no differences between plants grown under different light environments were found (Kharma et al., 2005).

For variable biomass accumulation in tomato plants grown in greenhouse two different plastic films, no differences between were found on the treatments. ^{Alcántar et al. (2003)}, found a total of 482 g of biomass in tomato plants 75 DDT These values are consistent with those found in the experiment as during the sixth sampling, biomass values were found in 316.02 g for plants grown under conventional cover and 327.87 g for plants grown under CIQA cover, and the seventh sampling results were 508. 614. 93 g 35 g respectively. ^{Shaheen et al. (1995)} indicate that as the radiation decreases, so does the dry weight, which was not reflected in this experiment, as no differences between biomass accumulation cultivate tomato plants under different plastic covers were found.

This indicates that, although, there were different values of radiation, these were within the limits of radiation necessary for the proper functioning of tomato plants grown in the greenhouse with the film CIQA. ^{Choe et al. (1988)} noted that, the dry weight and leaf area are higher than 28 °C than at 23 °C, in this case with general values of temperature above 28 °C, no differences were found for this variable.

By assessing the size of the fruits was found that 37.5% of the fruits of conventional greenhouse were classified as large, 52.5% as medium and 10% smaller, while the fruits developed under the CIQA plastic, 80% were large, 20 % medium, and no fruit for the category girl appeared, the size of the tomato fruit is covered by the import of assimilates and water and is determined by both cell number and size, as well as cell elongation during period of rapid growth (^{Ho, 1996}).

Table 2 Classification of size of tomato fruits grown in the greenhouse under different plastic films according to the NMX-FF-031-1997-SCFI. 

No differences in performance were found per plant using different plastics, being 30.4 and 33.8 kg m-2 for greenhouse plants with conventional plastic and CIQA plants respectively, these values are above the 26.2 and 19.2 kg m-2 which is found by evaluating different varieties of greenhouse tomato in a shorter harvest (^{Grijalva et al., 2004}). According to ^{Khah et al. (2006)} at temperatures of 27.8 and 33.1 °C higher yields for all treatments were found individually to obtain a total yield of 5 106.3 g per plant, as it is considered that favourable conditions for growth were taken for this study case during these periods, maximum temperatures were between 26 and 27 °C to 37 °C, and yields for greenhouses were 8 and 8 906.8 020.2 g per plant in a shorter period.